#include <iostream>
using namespace std;
int n, tmp, now, ans;
int main() {
    cin >> n;
    for(int i = 1; i <= n; i++) {
        tmp = i;
        while(tmp != 0) {
            now = tmp % 10, tmp /= 10;
            if(now == 1) ans++;
        }
    }
    cout << ans << endl;
    return 0;
}